We need to stop Cloudflare.
Imagine a world where all ISPs didn't let you spoof IP address. And, controversially, one where ISP customers had to pay for their SmartToaster's outbound DoS.
And better - if a service that started by using this got large enough, they could spin out on their own with no ties to the original platform.
Though of course CloudFlare protects booters as well, but I'm willing to buy their philosophical argument.